Conventionally, as a plastic cage for a radial bearing used in the change gear support part or shaft support part of an automobile transmission, there is known a cage which is injection molded by a radial draw mold (which is hereinafter called also a radial draw cage. See, for example, the patent document 1.), or a cage which is injection molded by an axial draw mold (which is hereinafter called also an axial draw cage. See, for example, the patent document 2˜4.).
As shown in FIG. 4, a cage 101 molded according to a radial draw system includes a pair of annular rim parts 103 spaced axially from each other and arranged coaxially, multiple pillar parts 110 connecting together the paired rim parts 103 in the axial direction and arranged at specific intervals in the circumferential direction, and pocket parts 120 each defined by the paired rim parts 103 and peripherally adjoining pillar parts 110 for holding a rolling element (for example, a needle or a cylindrical roller) rollably.
As shown in FIG. 5, in the radial draw cage 101, the outside diameter of the rim part 103 is larger than the outside diameter of the pillar part 110 and the radial thickness of the rim part 103 is larger than the radial thickness of the pillar part 110.
Meanwhile, as shown in FIGS. 6 and 7, a cage 1 molded according to an axial draw system includes: annular large-diameter rim part 5 and small-diameter rim part 7 spaced axially from each other and arranged coaxially; multiple pillar parts 10 connecting together the large-diameter rim part 5 and small-diameter rim part 7 in the axial direction and arranged at specific intervals in the circumferential direction; and, pocket parts 20 each defined by the large-diameter rim part 5 and small-diameter rim part 7 and peripherally adjoining pillar parts 10 for holding a rolling element (for example, a needle or a cylindrical roller) rollably.
As shown in FIG. 8, each pillar part 10 includes an extension portion 11 extending axially between the large-diameter rim part 5 and small-diameter rim part 7, an inside projecting portion 12 projecting from the radial inside of the extension portion 11 toward the large-diameter rim part 5 (outward in the axial direction), and an outside projecting portion 13 projecting from the radial outside of the extension portion 11 toward the small-diameter rim part 7 (outward in the axial direction).
The extension portion 11 is connected to the axial-direction inside surface 5a of the large-diameter rim part 5 and the axial-direction inside surface 7a of the small-diameter rim part 7. The inside projecting portion 12 is connected to the inner peripheral surface 5b of the large-diameter rim part 5. The outside projecting portion 13 is connected to the outer peripheral surface 7b of the small-diameter rim part 7. And, the inner peripheral surface 5b of the large-diameter rim part 5 includes an axial-direction inside portion 5c axially overlapping with the inside projecting portion 12 and an axial-direction outside portion 5d not axially overlapping with the inside projecting portion 12. Also, the outer peripheral surface 7b of the small-diameter rim part 7 includes an axial-direction inside portion 7c axially overlapping with the outside projecting portion 13 and an axial-direction outside portion 7d not axially overlapping with the outside projecting portion 13.